M8/M20 - Takahashi Sky-90 @f/4.5, QHY-9 mono CCD cooled to -35 deg C
Hey all
It's been quite a while since I bought the QHY-9, and I still haven't managed more than two nights with it. I've just managed to adapt some hardware to get the metal back distance from the reducer correct with the QHY-9 filter wheel in place. I had it out for a little while last night on the Sky-90 and produced this Ha effort before the moon came up at around 8:00pm. Not long, in other words.
Oh well, can't wait until the new moon weekend coming up where I'll head down south with a few friends and image the night away. I'll also be starting to run the LRGB filter set soon. Can't wait for some colour...
M8/M20 in Ha - Takahashi Sky-90 @f/4.5, QHY-9 mono CCD cooled to -35 deg C
Looks good Chris, although the moon shouldn't bother you to much with the HA filter in place. Pointing straight at it might be a problem though. Good to see you back on the horse. Well done.
Yeah, I know Doug. I spend most of the afternoon setting it up and by 8:00pm it was getting a bit chilly, and I a bit tired. Long week. No matter, a good 3 days in dark skies soon with good friends, a bottle or six and a Honda gennie....
What's the LRGB performance of the 90 like with the reducer in? Any CA at all..? I only ask because I have always toyed with the idea of getting a Sky90.
Don't know about its true CA performance. I really haven't tried the RGB set yet. That'll be what I do on the coming new moon w/e. Obviously it's only a doublet, but visually, at least, there is very little colour on brighter objects. Then again, I probably need to compare it to your AP, and far superior filter set, to really know. I do like the Sky-90. It was, surprisingly, out of collimation when I bought it but I've twiddled that a bit and think that it's better for it. They are, I hear, a little susceptible to "transport issues". That's OK - once i'd corrected it a little it's stayed that way ever since. I'll do a ful LRGB set on this same object set weekend after next and let you know.
Classic composition with all the right ingredients Chris. Well done. I do feel the black point is too low and needs to be raised to improve the contrast along with presentation of detail. Most of the data currently resides in the middle of the histogram (midtone area) which is the reason why the dark knots/globs are grey as opposed to being dark, or near black. Leaving the black point as is does provide a natural warm feel to the image however. Take the comments with a pinch of salt. Providing you're happy with it, that's all that counts.
I did leave the black point where it was, not knowing how the image was going to be affected by uploading to here on IIS. Typically one loses some measure of luminosity I've found. I compare the same local image in my browser and the one you're seeing, side by side, and it looks different just as a function of being in a different place. I agree with you wholeheartedly though, I usually prefer the shadow areas to be a little darker so I probably shouldn't pump the luminosity so much to compensate.
I'm not certain that this will be any better at this resolution, but here's another go.
Last edited by Omaroo; 01-07-2010 at 04:37 PM.
Reason: Slight adjustment
Yes, frustrating with internet browser support for colour spaces. If you're soft proofing in Photoshop, you should get a pretty close match before saving as a jpeg. (View | Proof Setup | Monitor RGB), then hit Ctrl+Y to active it. This assume that your monitor's RGB has gone through the calibration process.
Again, good work. Adding some RGB would be icing on the cake, but you probably won't be able to blend 100% of the Ha data as it will be too strong resulting in colour shifts. No harm in trying however as that's part of the fun of processing!
Thanks once again Jase You set a great example to we who are learning. Thank you!
I'm looking forward to a nice dark sky location weekend after next where I'll be trying my hand at accumulating RGB colour data for this object. Managing RGB lights and darks is going to be an interesting exercise. Can't wait to give it a go! I might leave Ha out of it for a bit until I gain more colour experience using a mono camera. Glad I took the leap though.
Very nice indeed Chris!
I have to agree with Jase in that your original image, the black point was too high with not enough contrast.
You're newly adjusted version is on the money.
I've heard in the past that some have sold their Sky90's and not persevered with getting the right gear, spacings etc to get them sorted for the large format cameras.
You've done a great job of this and shown what the 90 is capable of.
Really look forward to the added RGB as well.
Great fov... gotta love this time of year!!
Rich - yes, it's a bit of a chore to get the 90 humming, and I think that I'm nearly there. I now have a false star which I'll use to statically adjust the Tak a little more. Then, a final star test and tweak. The new model of the Sky-90 reducer/flattener seems to be doing the job pretty well. I have a metal back distance of nigh-on 72.2mm to the sensor plane, so it's bang-on according to the documentation. I can't wait to do some colour work with the Sky/QHY9 combo. I'd like to get a properly parfocal set of 2" LRGBHaSIIOIII filters one day. That'd be nice - not to have to refocus all the time.
Gday Chris very nice work top image, look forward when you add colour too, I'm in the same boat building up to a RGB run . Congrats on the Sky90 too great little scope
I'll also be starting to run the LRGB filter set soon. Can't wait for some colour... 
No matter, a good 3 days in dark skies soon with good friends, a bottle or six and a Honda gennie.... 
I also want to get the Nikkor 105mm f/2.5 going on the QHY-9 for a few ultra-wide shots in Ha.
. Congrats on the Sky90 too 
